NJ audited 2014 taxes and now my brother owes $1115 from a calculation error that he didn't do. What is the software guarantee for the software's error?

My brother used my 2014 Premier turbotax desktop software to prepare his taxes. I reviewed as best as I could his taxes when he was done to verify he added his information correctly and that the calculations were correct. He worked in NY for part of the year and paid for NY state taxes while living in NJ. For his 2014 NJ return, he got a refund but was audited within the past month by NJ. After providing his federal, NJ and NY state taxes, and W2s, he just got a letter saying he owes $1155 because of an error in the NJ tax form. The schedules A&B (NJ gross income tax) correctly calculated that the credit for income or wage taxes paid to other jurisdictions should be $926, which was verified by the auditor. However, in the NJ-1040 form, line 41 for the credit is listed as $1852 (double the amount that was in the schedules A&B). Because of that error, he owes $927 and interest of $182 from 16-apr-15 to 15-Mar-18 and a penalty of $46. I don't believe that this is result of his failure to input the correct info. What can be done since I am not sure what is involved in the accurate calculation guarantee.